a) Technical Field of the Invention
The present invention relates to an improved structure of a piston for air-filing device by making use of air pressure formed as a result of the reciprocation action of piston within the cylinder to urge an air-tightness disc mounted at the top of the piston to close rapidly and to open instantaneously.
b) Description of the Prior Art
FIG. 6 shows a conventional piston structure of an air-filing device, which employs high temperature resistant, and wear-resistant TEFLON (trademark of a plastic that stops things from sticking to it) material as piston cylinder ring. As the TEFLON material is highly flexible, it can be easily mounted to the piston. Thus, in conventional piston, circular shape TEFLON is directly mounted at the external surface of the piston to use as a cylinder ring for air-tightness.
As shown in the conventional cylinder piston apparatus A1, after the TEFLON material wears out, minute gaps may form between the cylinder wall A3 with the piston. Thus, air tightness cannot be obtained. If air leakage or the insufficient pressure is found in the air filing device, the entire air-filing device is damaged. This is one of the drawback of the conventional piston apparatus.
Furthermore, when the piston reciprocates within the cylinder, it is necessary to have an air-inlet valve apparatus A4, facilitating the entry of air, and then the air is compressed, and is formed into air pressure to be released. Other than the air leakage and insufficient air pressure as a result of wears of the TEFLON, the air inlet valve apparatus is also another drawback needed to be overcome. It is often that the air inlet valve body A41 is deformed, worn out, or spring A42 fatigue which cause a malfunction of opening or closing of the valve body. In particular, when an object enters and blocks the air inlet valve apparatus, the flowing of air is not smooth or the flowing-in air is insufficient. Thus, the drawbacks of the conventional air-filing device mentioned above have to be overcome.